PSIV-7 - Effect of maternal infection and dietary supplementation of isoflavones on offspring postnatal immune function

The objective was to determine the effect of maternal infection and dietary supplementation of isoflavones during gestation on offspring immune function. First parity gilts (n = 24) at gestational day (GD) 65 were allotted to one of three treatments: uninfected and fed a diet devoid of isoflavones (CON), infected with porcine reproductive and respiratory syndrome virus (PRRSV) and fed the control diet (POS), or infected with PRRSV and fed a diet supplemented with 1,500 ppm soy isoflavones (ISF). Gilts were inoculated intranasally with saline or 2.5×10⁴ TCID₅₀/mL of suspended live PRRSV (NADC₂₀ strain) on GD 70. At farrowing, 4 offspring pigs weighing closest to the litter average were selected for postnatal immune challenges. Innate immunity was determined by serum TNF-α concentrations after lipopolysaccharide (LPS) injection (5 µg/kg BW) on postnatal d (PND) 52. Adaptive immunity was determined in the same pigs by peripheral T cell population shifts following vaccination against porcine circovirus-2 on PND 59. Whole blood was collected on days post-vaccination (DPV) 0, 7, and 14 for T cell phenotyping. In the innate immune challenge, all groups experienced increased TNF-α after LPS injection with peak response at 4 h, with ISF eliciting higher (P = 0.04) TNF-α concentrations than CON, and POS being intermediate. Also, ISF had higher (P < 0.01) TNF-α concentrations at both 0- and 8-h post-challenge compared with CON and POS. Prior to vaccination, ISF had elevated memory T cells and reduced total and naïve T cells (P ≤ 0.02). At DPV 14, the reduced total and naïve T cells persisted in ISF pigs. Overall, these data indicate that maternal PRRSV infection alone does not predispose pigs to an exaggerated immune response. However, maternal isoflavone supplementation during PRRSV infection altered offspring innate and adaptive immune responses.